For a facility including many load apparatuses, various technologies for suppressing utility energy consumed by load apparatuses have been proposed so far. For example, many load apparatuses such as lighting apparatuses, air conditioners and refrigerating apparatuses (refrigerators or freezers) are installed in a facility such as a supermarket dealing with food. In order to suppress utility energy consumed by such load apparatuses, an energy management system is provided and configured to control load apparatuses according to various conditions.
In general, a consumer of electricity makes an electricity supply contract with a power company. In a Japanese contract, contract demand is set to a largest value of maximum demand power for each month of a past year including a current month. Maximum demand power for a current month is obtained by measuring an integrated value (demand energy) of demand power (power consumption) per prescribed demand time limit (typically 30 minutes) to obtain demand power and by selecting maximum demand power from each demand power measured up to the current month.
For example, JP Pub. No. 2009-240032 accordingly discloses a demand control system. The system is configured to control respective power of lighting apparatuses so that the demand value (demand power) does not exceed a predetermined contract demand.
In a case where the integrated value of demand power (power consumption) is managed as stated above, if not having expert knowledge, a user cannot recognize whether or not an integrated value of power consumption changes suitably even if only the integrated value of power consumption is shown. If the management of power consumption is performed in accordance with a rule that is set to the energy management system, the user will believe that an integrated value of power consumption changes suitably.
In a case where a large change occurs in an external environmental condition (e.g., air temperature), there is a possibility that an operation that is not necessarily preferable for management of a facility is performed by load control because the energy management system performs a uniform control. For example, in a facility in which flat showcases are installed as refrigerating apparatuses, it is necessary to secure power for the showcases because each temperature inside the showcases requires to be maintained. That is, when the handling by the energy management system is difficult, users themselves require judging management for the case. However, if they have no expert knowledge, they cannot perform necessary management.